A nozzle chip is used, for example, in a liquid ejection head that ejects a liquid from ejection orifices. Examples of a liquid ejection head include an ink jet recording head that performs recording by ejecting an ink toward a recording medium such as a sheet of paper. PTL 1 describes a method of making a nozzle chip of an ink jet recording head.
The method of making a nozzle chip described in PTL 1 will be briefly described. First, an element substrate, which includes energy generating elements that generate energy used to eject a liquid from ejection orifices, is prepared. Next, a positive photosensitive resin layer including an optical absorption agent is formed on the element substrate. Then, the positive photosensitive resin layer is exposed to light, and thereby a pattern having the shapes of flow paths is formed. Next, a negative photosensitive resin layer, which serves as an ejection orifice forming member, is formed so as to cover the pattern, and the negative photosensitive resin layer is exposed to i-line light (wavelength 365 nm), and thereby an ejection orifice row is formed. Lastly, the pattern is removed, and thereby liquid flow paths are formed.
When forming an ejection orifice row on a nozzle chip by using the method described in PTL 1, there are some cases where it is required to expose to light a pattern that is larger than a field angle size, which is the size of the largest area over which an exposure apparatus can perform exposure. In such cases, a manufacturing method called “fractionated exposure”, which is described in PTL 2, may be used. With fractionated exposure, a pattern having a size larger than the field angle size is divided into portions smaller than the field angle size and arranged on a mask, and then exposure is performed. An ejection orifice row is formed by performing irradiation with light rays by using a mask having ejection orifice row patterns that form an ejection orifice row pattern of one nozzle chip when the ejection orifice patterns are connected to each other through a connection portion. A connection portion is usually a portion at which a nozzle chip is divided in a direction perpendicular to a direction in which ejection orifice rows are arranged, that is, in the longitudinal direction of the nozzle chip.